1. Field of the Invention
The present invention relates to a roll crossing apparatus for causing the upper and lower rolling rolls of a cross-rolling mill to cross each other in horizontal directions.
2. Description of the Prior Art
FIG. 8 is a side elevation view of an essential portion of a cross-rolling mill of the prior art, and FIG. 9 is a perspective view of a roll crossing apparatus of the mill of FIG. 8.
As shown, shafts 35 are rotated, as better seen from FIG. 9, through individual bevel gears 34 by individual motors 51. Then, screw shafts 32 threaded to nuts 33 are rotated through individual worm reduction gears 31. Thus, an upper cross head 29 and a lower cross head 30 fitted in guides 36 are moved in opposite pass line directions.
As these upper and lower cross heads 29 and 30 move, an upper work roll chock 25 and an upper backup roll chock 27, and a lower work roll chock 26 and a lower backup roll chock 28 revolve in opposite directions about the central portions of the upper and lower work rolls 21 and 22, as taken in the roll axis directions, to cause the upper work roll 21 and an upper backup roll 23, and the lower work roll 22 and a lower backup roll 24 to cross each other.
In the rolling operation, a rolled sheet S has its shape adjusted by regulating the cross angle and by bending the upper and lower work rolls 21 and 22.
The apparatus described above has the following drawbacks.
(1) Since the upper and lower cross heads 29 and 30 having considerable lengths are individually supported at two points along their lengths by two of the screw shafts 32, they typically have large thicknesses in the pass line directions. This makes it necessary to provide a wide window (i.e., the spacing between the inner side surfaces) for the housing 20 or deep grooves which are formed in the inner side surfaces of the housing 20 to accommodate the upper and lower cross heads 29 and 30. Unless the housing 20 is to have low strength and rigidity, it is necessary to further enlarge the size of the housing.
(2) Since the loads to be borne by the upper and lower cross heads 29 and 30 are applied directly to the screw shafts 32 and the nuts 33, these shafts 32 and nuts 33 have to be large which thus requires that the roll crossing drive train elements, such as the worm reduction gears 31, to be large.
(3) Each stand has to be equipped with as many as sixteen sets of screw shafts 32, nuts 33 and worm reduction gears 31; therefore, the apparatus is accordingly complicated and expensive.
(4) When an existing parallel rolling mill is to be reformed into a cross-rolling mill having a high ability to control the sheet shapes, the housing 20 has to be remarkably worked.